334 



THE IRRIGATION AGE. 



through the medium of the leaves ; that is to say, trans- 

 pired through the stomata or mouths of the leaves. 

 Indeed, there is no other way by which water can enter 

 into the plant. It is a solvent for plant food, and the 

 plant having absorbed the food, rejects the water by 

 transpiration. 



The reader will find in Chapter V an experiment 

 made by Professor Williams of Vermont with an acre of 

 forest containing 640 trees averaging S 1 /^ inches in 

 diameter and 30 feet in height, having an average 

 of 21,192 leaves on each tree to transpire water during 

 ninety-two days. 



It was discovered by careful experiment that such 

 an acreage of trees drew from the soil and evaporated, 

 or transpired by way of the tree leaves, 2,852,000 pounds 

 of water during ninety-two days, or 1.426 tons, the 

 evaporation or transpiration being calculated as going 



View in Perrine's Vineyard, Showing Loaded Grape Vines. Mr. I. B. 

 . Perrine is central figure in group. The figure to left is Mr. 

 G. D. Aikin ofthe Oregon short Line Railway. 



on twelve hours per day, inasmuch as it is almost im- 

 perceptible at night. This leaves a very large balance 

 of the 4,526 tons unconsumed by the trees, and even 

 assuming that the leaves transpired water during twen- 

 ty-four hours there would still be 1,674 tons to the good 

 unutilized by vegetation. 



Carrying the calculation still further, let it be 

 assumed that the evaporation from the soil was 1,000 

 pounds per hour and that such evaporation occurred 

 every hour of the twenty-four, and there would be still 

 remaining unutilized for any known purpose 570 tons 

 of water. There would remain a much larger quantity, 

 for the estimate of evaporation could not exist in a for- 

 est, and not under any circumstances at night. More- 

 over, evaporation from a freshly plowed soil does not 



reach 1,000 pounds per hour, even without vegetation to 

 retard it. 



Recurring to the sunflower experiment (Chapter V). 

 An acre of sunflowers three and a half feet high, esti- 

 mating 10,000 of them to the acre, which would be 

 crowding them, with their great broad leaves, would 

 transpire during twelve hours every day for ninety days 

 810 tons of water drawn from the soil. It will be per- 

 ceived that the 4,526 tons of irrigating water or rain- 

 fall are still practically intact, and it may occur to the 

 mind of the ordinary reader that forty inches is alto- 

 gether too much water to put on or into the soil for 

 any profitable or needed purpose. If not, what becomes 

 of it? It is not utilized by vegetation of any sort. 

 Even sugar cane, which possesses an insatiable thirst, 

 would repudiate such gluttony. 



The fact is, about three-fourths of this water is 

 wasted fed to run-off, seepage and drainage. It is 

 put into the soil to kill the plants eventually instead of 

 nourishing and giving them life. 



Government experts say that out of a possible forty 

 inches of rainfall 50 per cent of it is lost in running 

 off* or out of the land, and 25 per cent disappears 

 through evaporation. If this is correct, then there are 

 left ten inches to be utilized by the crop, whatever it 

 may be, and according to our calculation that amount 

 is ample for plant growth from the planting to the 

 harvest if irrigation is practiced as it should be. 



There is this to be also considered, that rainfall 

 does not mean a precipitation of a certain number of 

 inches of water during the growing season when needed 

 more than at any other time, whereas irrigation does 

 mean that very thing. Taking four months of the 

 year as the growing period, that is to say, May, June, 

 July and August, where summer is the seedtime and 

 harvest, or January, February, March and April on 

 the Pacific Coast and semi-tropical regions, the mean 

 monthly precipitation of water at forty inches per an- 

 num 1 would be one-twelfth of the annual supply, or 

 three and one-third inches, a total for the entire grow- 

 ing period of thirteen and one-third inches. 



When it comes to crop requirements averages are 

 to be disregarded, but assuming it* to be true. that the 

 forty inches of rainfall are evenly distributed during 

 the growing season, as above specified, then a crop can 

 be grown to maturity on thirteen and one-third inches ; 

 indeed, it can not be imagined that the entire annual 

 rainfall is precipitated upon the soil during the four 

 months specified unless rice culture be contemplated. 

 With thirteen and one-third inches of water distributed 

 through the growing season the soil receives 1,508 tons 

 of water per acre, which, by referring to the cases of 

 the forest and the sunflowers above given, will more 

 than satisfy the requirements of those plants ; in fact, 

 nearly two acres of sunflowers can be amply provid- 

 ed for. 



Now, what becomes of the remaining twenty-six 

 and two-thirds inches of the assumed forty inches? 

 The 3,018 tons of water on our acre? In the opinion 

 of the writer that water has gone down to raise the 

 ground water uncomfortably close to the root zone, 

 where it will do damage, has "ran off or drained off. 

 It is certainly wasted unless the excess is intended to 

 irrigate several more acres further down some slope, or 

 is to be pumped out from wells and used over again. 

 In that case, why put so much water on the soil if 

 agriculture be the object and not the water supply 

 business? 



